Environments for spaces of many types must be accurately controlled. For example, it is routine to control temperature and humidity in occupied spaces. The environment within spaces used for storing or manufacturing products and apparatus of many types often must be controlled as well. For example, storage or manufacturing areas for electronic equipment often have temperature, dust and chemical contaminants, and humidity limits that must be closely observed. Over the years, a variety of reliable and effective control systems have been developed for meeting these requirements. However, for a variety of reasons these control systems sometimes fail, requiring human intervention. Further, it is often necessary to provide an historical record of these failures and also of proper operation.
For example, heating plants and air conditioners can fail because of a tripping circuit breaker, a short outage of fuel or electricity, or failure of a critical part of the system. In some cases these failures are nuisances only. In others, they may cause significant economic loss or may even threaten life or health of animals or humans. Consider the problem of controlling laboratory animals"" environment. After a period of time, an experimenter may have a significant investment of time and money in ongoing experiments that will be lost if prescribed environmental conditions for the animals are not maintained. These laboratories may not be staffed around the clock, so that a defect in the space""s environment may not be noticed for a period of many hours.
An even more important situation is controlling the environment in which food is stored. The need for food to have safe levels of various pathogens and contaminants can hardly be overstated. Anyone who has visited a modern supermarket knows of the sophisticated environmental controls for temperature and sometimes humidity as well, in produce displays. Yet these are nothing more than mechanical and electrical systems having large numbers of critical components, any of which are liable to failure. Although infrequent, failures can occur that affect the quality of the food. Refrigeration failures that persist for several hours are extremely costly, in that the food spoils and must be thrown out. Even worse, if the failure is intermittent the food may spoil in a way not readily noticeable, but that results in unhealthy food. For example, in a variety of inadequately refrigerated food products, E. coli and salmonella bacteria can grow to a level that may be harmful and yet leave no visual indication this has even happened. Even if the cooling and heating systems operate properly, improper loading of storage spaces, doors that don""t close properly, operator error, etc. can affect food safety and quality.
The system to be described in this patent application has been developed primarily to monitor the temperature environment for perishable foods, but the principles can be easily extended to other types of things and creatures as well. Experts generally regard perishable food produce held at a temperature above 41xc2x0 F. (5xc2x0 C.) for more than 4 hours total as unsafe to eat. Dangerous pathogens will not usually proliferate in food that is held between 38 and 41xc2x0 F. (4xc2x0 C.) but quality may be affected by spoilage, wilting, etc. So the standard for safe storage of perishable food products now sets 33-38xc2x0 F. (0.5-4xc2x0 C.) as the proper range for storage of these materials.
The federal Food and Drug Administration (FDA) and the Department of Agriculture (DA) are in the process of setting standards for storing fresh perishable foods. These standards are defined by rules identified by the acronym HAACP (Hazard Analysis of Critical Control Points). HAACP is currently under modification, but essentially specifies a set of required activities for food storage. These activities include:
specifying temperature limits for various types of food products
monitoring temperature of food products having temperature limits
notifying an operator when limits are exceeded
correcting the problem when temperature limits are exceeded to assure safety
documenting the preceding activities, and
verifying all of the preceding activities
At the present time, operators of food storage and marketing facilities perform these steps manually. Thermometers are placed in food display cases, and are periodically read and recorded manually. The people in charge of the facility take what seems to be the appropriate actions whenever a temperature is read as out of the stated limit, and then document and verify the corrective action.
This approach has a number of disadvantages. It is labor-intensive and therefore expensive. Since most of the time there is no problem, it is easy to lose the discipline needed to make the readings at the scheduled times. Since humans are involved, it is likely that the sensors will not be read as scheduled or will be read incorrectly. Manual reading cannot be done frequently enough to avoid loss of food quality or even pathogen growth when out of range temperatures occur. The corrective actions taken may not immediately correct the problem. For example, a corrective action of reducing the set point temperature will not easily solve the failure if the reason the temperature has risen above the limit because the case is overfilled or a cold air duct is obstructed. Manual readings may not detect brief temperature excursions past the limit, say those caused by defrosting. On the other hand, when manual readings do detect these excursions the response may be to take unneeded corrective actions.
Where sensors are not visible from outside the display case and must be read with the door open, further error in the readings may result. All of these conditions can result in erroneous monitoring of the conditions within food storage spaces.
Of course, similar considerations are present for freezer cases and hot food cases. In fact, hot food cases have the potential for very rapid pathogen growth if the temperature falls much below a safety temperature.
The result of all these considerations is that monitoring the storage environment generally and the temperature in particular for various foods is a difficult and expensive activity that may often result in inaccurate detection of food condition. If healthful food is detected as bad, this leads to unnecessary discarding of food and substantial unnecessary expense. If bad food is detected as good, this may give rise to a serious health issue, with enormous consequences both for consumers and the businesses in the food supply chain.
Accordingly, an alternative to manual sensor monitoring is advantageous. There have been systems described in the past that provide alternatives to manual monitoring. Among these, U.S. Pat. Nos. 5,900,801 and 5,939,974 (both to Heagle et al.) teach a comprehensive system for monitoring food preparation, storage, and delivery. A number of patents described in the Heagle patents also disclose environmental monitoring systems.
We have developed a system for monitoring a varying and measurable parameter level at a plurality of points within a space. We expect that the users will usually chose to monitor the quality or condition of products stored in the space. We intend the term xe2x80x9cproductxe2x80x9d to include a wide variety of goods, food products, and material whose quality or condition is affected by some parameter or condition of the product""s environment such as temperature, humidity and moisture content, vibration, airborne contamination, microbial contamination, etc. The application we presently prefer for the system is to monitor the temperature within food storage spaces.
This system includes a plurality of product condition sensors each having an associated identifier code. Each sensor is to be placed in physical proximity to a product so as to measure the product condition parameter level. Each sensor provides a sensor signal encoding the measured parameter level.
We find it convenient to use a small computer along with appropriate software and some sort of interface for communicating with the sensors to provide the remaining elements of the invention.
The computer conveniently provides a memory as a further element of the system. The memory is first, for recording at least one predetermined parameter value in association with each sensor identifier code, and second, for recording in association with each predetermined parameter value, a set of message code strings for a plurality of messages. These message code strings encode printable messages providing status information or suggesting remedial action for a user when an out-of-range condition is detected for the condition sensed by the sensor. Thirdly, the memory records application software whose execution causes the computer to provide the desired functionality of the invention.
The computer""s display component functions as a display unit in this invention for providing a visual display of messages responsive to a display signal encoding the set of message code strings.
When the computer executes the application software recorded in the memory, it becomes physically and functionally a data analyzer. The computer/data analyzer element receives the sensor signal from a sensor and a predetermined parameter value recorded in the memory in association with that sensor""s identifier code. The data analyzer then compares the measured parameter value encoded in the sensor signal with the received parameter value associated with the sensor""s identifier code. Responsive to a predetermined relationship between the measured and recorded parameter levels, the data analyzer retrieves from the memory the set of message code strings associated with the recorded parameter value, and encodes the retrieved set of message code strings in a display signal provided to the display unit.